Here's a quick guide for one way to do it:
1. Go to settings
2. Click on your name
3. Scroll down to iCloud Backup
4. Make sure it's on (Backups generally happen when connected to Wi-Fi and on charger
5. Optionally, select Backup over Cellular
6. There is also a Back Up Now option
Hope this is helpful
14PM - iOS 17ß2